The present invention relates to a labelling system and in particular to a roll fed labelling process in which labels are scanned and cut in registration prior to their application to a bottle or other container.
In the conventional roll fed labeling system, labels are scanned by an electronic scanner designed to detect a change in coloration between a triggering mark and the adjacent label graphics. For the system to work properly, there must be sufficient opacity of the triggering mark color; sufficient contrast between the triggering mark color and the adjacent graphics and sufficient spacing between the triggering mark and the adjacent graphics to that the scanning equipment does not confuse the one for the other.
It is possible to improve detection accuracy by interposing a colored filter between the mark and the detector, the particular color chosen to enhance contrast. This is not convenient because it entails changing filters and adjusting sensitivity levels each time there is a change in the material being scanned. This is especially so for bottlers who must change labels periodically.
Bottlers experience considerable downtime resulting from problems associated with the conventional scanning system. This is partially due to the increased use of more complex graphics and more frequent packaging changes, which require realignment and adjustment of the scanning equipment. In addition, the use of stylized, distinctly designed, bottles often requires small labels because of the contours of the bottle, thereby reducing the spacing available between a triggering mark and adjacent graphics. Finally, the increased use of promotional banners across the label to announce special offers and promotions require sharp contrasts with the remainder of the label thereby potentially interfering with the ability of conventional scanning equipment to distinguish the triggering mark from the graphics or confusing the banner or a portion thereof for the triggering mark.
It is known from U.S. Pat. Nos. 4,467,207 and 2,888,570, for example, to provide the product being scanned with a mark comprising fluorescent material and to irradiate it with ultraviolet light with a wavelength of about 365 nanometers. The mark converts the UV light to a different wavelength which is predominantly visible light and is detected by a suitable detector. As a general rule, scanning systems for labels and the like operate in ambient light which may cause some colors, such as certain greens and yellows, to emit light of much the same wavelength as that emitted by the mark. This results in high levels of interference or noise making it difficult for the detector to detect the mark. This interference or noise will depend upon the colors used in the label, and exacerbate the problem of adjusting sensitivity levels every time a label type is changed.
Further difficulties stem from the high operating speeds of modern bottling machinery, which demand speed and precision in the detection of the triggering mark to ensure that the labels are cut at the correct position.
In view of the above, it is the principle object of the present invention to provide an improved label scanning system and label which is far less sensitive to the label graphics for registration and alignment.
A further object is to provide such a scanning system and label that requires a nominal change to existing labeling equipment and can be readily adapted to existing bottling lines.
The above and other objects and advantages are attained in accordance with one aspect of the present invention by providing a roll of labels printed with conventional inks and wherein the demarcation between the individual labels is registered to associated triggering marks printed of an ink containing a luminophor, for example a fluorescent brightening agent. The label roll is irradiated with electromagnetic radiation of a first frequency, for example modulated ultraviolet light which causes the triggering mark to emit correspondingly modulated radiation of a different frequency, such as visible light. The detection of the modulated visible light is thus independent of the relationship between the triggering mark and surrounding graphics so that no color change is required to produce a sharp contrast to set off the triggering mark from the remainder of the label. Upon detection of the triggering mark a cutting assembly is activated to separate an individual label from the roll.
Preferably, the modulation is at a modulation frequency which is outside the frequency of visible light and may be in the kilohertz range, conveniently about 33 kHz.
Even when such a modulated UV light source is used, there may be interference from certain colors which are slightly fluorescent and so will also convert the modulated UV light into modulated visible light, in the same way that the triggering mark converts it. This can lead to difficulties in setting the sensitivity of the sensor so that it will detect the triggering mark but not respond to the background colors. Clearly, the signal to noise ratio, i.e. the amount of light reflected from the triggering mark as compared to light reflected from neighbouring parts of the label, will be increased by increasing the amount of luminophor material in the triggering mark. The fluorescent optical brightening material is very expensive so it is desirable to minimize the amount used. On the other hand, if there is insufficient optical brightening agent in the triggering mark, the sensor may not be able to detect it against the background xe2x80x9cnoisexe2x80x9d or interference. The problem is exacerbated where, as is usual, the rolls of labels are produced by an independent supplier and it is left to the bottler to adjust sensitivity levels to suit the different labels and compensate for different colors and color combinations.
According to another aspect of the present invention, a method of producing labels for applying to containers in the manner defined in the first aspect, includes the steps of producing a roll of said labels with said triggering marks each registered to a label, scanning the roll of labels using radiation at a first frequency, for example UV light, and obtaining a measure of the amount of radiation at a second frequency, for example visible light, emitted by a said triggering mark in response to irradiation by the radiation at the first frequency; comparing the measured radiation with a reference level representing a maximum level of radiation at the different frequency emitted by colored parts of the label when irradiated by said radiation at the first frequency and, if the radiation from the triggering mark does not exceed said maximum by a predetermined margin, increasing the amount of luminophor material in the triggering mark.
The reference level may be derived by measuring such radiation, e.g. visible light, emitted by selected colored portions of the label when irradiated by said radiation at the first frequency. The colored portions selected may be those which will subsequently be scanned by the sensor.